In wireless (air interface) communication systems, signals transferred from a plurality of mobile devices arrive at the base station with different propagation delays and different power. Large propagation delay and power difference often result in significant loss of signal at the base station. One method for the base station to control the propagation delays and power levels of the signal from mobile devices is to have each mobile device send a predetermined pseudo random code identifying itself on a defined ranging time slot or channel. These codes, or ranging signals are used by the base station (which could include any suitable distant end transmission point) to determine the time delay and transmission power level of the mobile device.
Since the base station does not know which code is being sent by the mobile device, the base station must isolate the sub-channel codes for each mobile device. One method of isolating the code from a mobile device is to match the incoming signal against a known signal in order to determine which code is being sent. However, because there are many possible codes and because they are not arriving at the base station with a known time (phase), the solution to the problem becomes a two-dimensional calculation, i.e., first the system must check to see if the signal contains a known code at a first time (first phase). If not, then the system must repeat the process for successive time slices (phases) to see if a particular code is being received. This is time consuming and requires high processor resources. Besides, the channel phase ambiguities acting on ranging channel will significantly deteriorate the measurement precise of propagation delays.